Electrophoretic separations of biopolymers and small molecules are critically important in modem biology and biotechnology, playing a central role in such techniques as DNA sequencing, protein molecular weight determination, genetic mapping, and the like. A particularly preferred electrophoresis format is capillary electrophoresis (CE), where the electrophoresis is performed in a capillary channel having a small internal diameter, e.g., between 5 and 100 μm. In many applications, capillary electrophoresis results in enhanced separation performance over traditional slab-based formats because the superior ability of the narrow-bore capillary to dissipate Joule heat allows for the use of high electrical fields thereby resulting in fast separations in which the effect of analyte diffusion is reduced. In addition, capillary electrophoresis is well adapted to automation because of the ability to automate the steps of sample loading, analyte detection, and replenishment of the separation medium.
Certain commercially important applications of capillary electrophoresis require exquisite separation efficiency. For example, in DNA sequencing separations, plate counts of 20 million plates per meter may be required. In order to achieve this kind of performance, everything possible must be done to reduce instrumental effects that can lead to peak broadening and therefore lower separation efficiencies, e.g., peak broadening caused by the radial temperature profile within the lumen of the capillary, the sample injection volume, solute-wall interactions, siphoning, finite detection volume, and the like (e.g., Capillary Electrophoresis Theory and Practice, Chap. 1, Grossman and Colburn, eds., Academic Press (1992)). In addition, because of the high throughput requirements of large-scale DNA sequencing operations, any measures taken to increase the separation performance of the electrophoretic analysis preferably will not substantially reduce the speed, and therefore the throughput, of the process.
Therefore, any further understanding of the mechanisms underlying peak broadening and techniques for reducing the impact of such mechanisms on the performance of CE separations without sacrificing the speed of analysis would be an important contribution to the field of capillary electrophoresis and related applications.